Learning Targets Please write at the top of your notes: Explain the difference between autosomal and sex- linked genes and how sex-linked genes produce different inheritance patterns in males and females.

Blood Type and Sex Linked Inheritance

The Classic Example of Codominance in Humans is BLOOD TYPE Gene that controls ABO blood type codes for an enzyme that makes a glycolipid on blood cells Two alleles (IA and IB) (call them “A” and “B”) are codominant Third allele (IO) (call it “O”) is recessive to A and B

Possible Genotypes for Blood Types If the Phenotype: A Genotype(s): AA, AO If the Phenotype: B Genotype(s): BB,BO If the Phenotype: AB Genotype(s): AB If the Phenotype: O Genotype(s): OO

https://www.polleverywhere.com/multiple_choice_polls/wjRAgHqnWW0PtrL

Your blood type is determined by A and/or B proteins on red blood cell surfaces

https://www.polleverywhere.com/multiple_choice_polls/kpKP5KUeKfMbXrC

Blood Tests are done by adding antibodies to the sample Which blood type clots with both anti-A and anti-B? _____ Which blood type doesn’t clot with anti- A or anti-B? _____ AB O Do you know what YOUR blood type is?

The Rhesus Factor You are either R(+) or R(-) for the Rhesus Protein A problem for Rh (-) moms … What if baby is Rh (+)? Doctor can give Mom a shot (Rhogam, at about 28 weeks) that removes or hides R(+) cells from Mom’s bloodstream

Cross: ____ X ____ BO OO B O O BO OO O OO BO A Real Problem: Mom is Type B, Dad is Type O … Baby is Type AB. Is this possible? Cross: ____ X ____ BO OO mom B O O BO OO SORRY! NOT POSSIBLE! O OO BO

Sex Chromosomes: the 23rd pair in humans All others (1- 22) are called autosomes Boy Girl

The Sex Chromosomes  The “X” Chromosome The “Y” Chromosome Has essential genes Can’t live without it! Female 23rd pair = XX (one usually deactivated) The “Y” Chromosome Few genes Determines if testes develop Male 23rd pair = XY

What’s the probability of having a boy or girl? XX XY X Y 50% 50%

Sex-Linked (X-Linked) Traits  Sex-Linked (X-Linked) Traits Sex-Linked traits are usually found on the X (not Y) chromosome (“X-linked”) Males are affected or not, no heterozygotes… WHY, do you think?

Some X-Linked Traits: Hemophilia (missing clotting enzymes) Colorblindness “Male-pattern” baldness Most are recessive**

Hemophilia Ability of blood to clot is impaired. The main treatment for hemophilia is called replacement therapy—giving or replacing the clotting factor that’s too low or missing. http://www.nhlbi.nih.gov/health/dci/Diseases/hemophilia/hemophilia_treatments.html

“The Royal Disease”

A hemophiliac man marries a healthy woman A hemophiliac man marries a healthy woman. What is the probability that they will have any hemophiliac children? 0% All sons healthy All daughters carriers

Colorblindness Red-green colorblindness- red and green are perceived as identical. Affects: 1 in 10 males in the US 1 in 100 females in the US Remember: Males have just one X chromosome. All X-linked alleles are expressed in males. http://wpcontent.answers.com/wikipedia/commons/a/a3/XlinkRecessive.jpg; http://www.medterms.com/script/main/art.asp?articlekey=7255

100% XcXc XY Cross: ____ X ____ Xc Xc X XcX XcX Y XcY XcY A man with normal vision marries a colorblind woman. What is the probability that they will have a colorblind SON?  Remember, Mom only shows if she is homozygous! XcXc XY Cross: ____ X ____ mom Xc Xc Focus only on SONS (not daughters)! X XcX XcX 100% (2/2) SONS Y XcY XcY

What do you see?

50% XbX XbY Cross: ____ X ____ Xb X Xb XbXb XbX Y XY XbY A bald man marries a woman whose father was bald. What is the probability that they will have a SON with male-pattern baldness?  If Mom’s father was bald, then he must have passed that X to her! XbX XbY Cross: ____ X ____ mom Xb X THE TRICK: Focus only on SONS (not daughters)! Xb XbXb XbX 50% (1/2) SONS Y XY XbY